|Year : 2021 | Volume
| Issue : 2 | Page : 125-129
Glomerular filtration rate changes in the first week of healthy full-term newborns
Ahmed A Monem1, Moftah A Hamid2, Hala M Abdel-Aal3, Shireen R Soliman1
1 Department of Pediatric, Damanhour Medical Institute, Damanhour, Egypt
2 Department of Pediatric, Faculty of Medicine, Al Azhar University, Cairo, Egypt
3 Department of Clinical Pathology, Damanhour Medical Institute, Damanhour, Egypt
|Date of Submission||11-Jun-2021|
|Date of Acceptance||01-Jul-2021|
|Date of Web Publication||10-Nov-2021|
MD Ahmed A Monem
Department of Pediatrics, Damanhour Medical Institute, Damanhour, Alexandria, 21515
Source of Support: None, Conflict of Interest: None
Background Renal function − as many other organ functions − is immature in the early neonatal period.
Aim A prospective study was carried out that aimed at determining serum creatinine and glomerular filtration rate (GFR) in apparently healthy full-term newborns (NBs) on the first and seventh days of postnatal life.
Participants and methods This study included 50 apparently healthy full-term neonates born to healthy mothers at Damanhour Medical Institute in AL-Behera governorate. Half of the neonates were males; 27 babies were delivered vaginally and the remaining by cesarian section. All NBs were subjected to a full assessment of history and clinical examination. Complete blood count, C-reactive protein, alanine transaminase, aspartate transaminase, and abdominal ultrasound were performed for all NBs. Serum creatinine and GFR were estimated on the first and seventh days of life. Maternal serum creatinine was determined for all mothers on day 1.
Results Serum creatinine showed a significant decrease on the seventh day. GFR was significantly increased by the seventh day of life. NBs’ serum creatinine showed a negative correlation with the postnatal age, while GFR showed a positive correlation.
Keywords: function, newborn, renal
|How to cite this article:|
Monem AA, Hamid MA, Abdel-Aal HM, Soliman SR. Glomerular filtration rate changes in the first week of healthy full-term newborns. Alex J Pediatr 2021;34:125-9
|How to cite this URL:|
Monem AA, Hamid MA, Abdel-Aal HM, Soliman SR. Glomerular filtration rate changes in the first week of healthy full-term newborns. Alex J Pediatr [serial online] 2021 [cited 2022 May 24];34:125-9. Available from: http://www.ajp.eg.net/text.asp?2021/34/2/125/330259
| Introduction|| |
The human kidney begins to develop in the fifth gestational week and starts to produce urine between the 10th and 12th week of gestation . Nephrogenesis is complete between the 32th and the 36th week of gestation, with most nephrons being formed during the third trimester of pregnancy . During pregnancy, fetal fluid homeostasis is maintained by the bidirectional exchange between the mother and fetus through the placenta and the only purpose of fetal renal excretory function is its contribution to the formation of amniotic fluid . During fetal life, nephrogenesis plays an important role in maturation of the glomerular filtration rate (GFR), which remains low even at the end of gestation .
Maturation of neonatal GFR depends on the development of renal blood flow (RBF). Fetal kidneys receive 2–4% of the combined ventricles’ output during the last trimester due to high renovascular resistance and the filtration fraction compared with a full-term newborn (NB) . After birth, a marked increase in systemic blood pressure and decrease in renal vascular resistance result in elevated RBF and a consequent increase in GFR. Vasoactive factors including renin, angiotensin II, glucocorticoids, NSAIDs, nitric oxide, prostaglandins, bradykinin, and endothelin play vital roles in the regulation and development of neonatal GFR .
GFR is the most useful measurement of kidney function . Creatinine clearance remains a widely used clinical parameter for evaluating GFR . The Schwartz formula correlates very closely to levels of creatinine clearance, and can be used to estimate GFR without urine collection . The simplicity of the Schwartz formula has led to its wide use in most neonatal units.
It is necessary for clinicians to track postnatal changes in GFR, so that they can recognize abnormal changes in kidney functions.
| Aim|| |
The aim of the present work was to determine GFR and serum creatinine levels in a group of healthy full-term NBs during the first week of life (days 1 and 7) and serum creatinine of the mothers at day 1 after labor.
| Participants and methods|| |
The study included 50 apparently healthy full-term neonates born to 50 healthy mothers at Damanhour Medical Institute in AL-Behera governorate, Egypt. The gestational age of the studied NBs ranged from 37 to 41 weeks, with a mean of 38.7±1 weeks. Half (50%) of the neonates were males, and an informed consent was obtained from the parents of NBs included in the study.
Ethical approval: this study was approved by the Medical Research Ethics Committee at Damanhour Medical Institute and an informed consent was obtained from children’s guardians.
NBs with congenital malformations, severe respiratory distress, premature NBs, low-birth-weight NB infants, NBs born to mothers with chronic illness, and those delivered with difficult labor were excluded from this study.
All NBs were subjected to a complete assessment of history and clinical examination.
Assessment of history included:
- Family history of hereditary diseases, urinary problems, and chronic illness.
- Maternal history included age, parity, previous pregnancy outcomes, medications, smoking, and history of chronic illness.
- Perinatal history included gestational age, presentation, onset and duration of labor, timing of rupture of membranes, and complications to the mothers and their NBs.
Examination included vital signs, color, Apgar score assessment, anthropometric measurements, and system examination.
- Complete blood count, C-reactive protein, alanine transaminase, and aspartate transaminase, all performed on the first day.
- Serum creatinine: determined on the first and seventh days of life.
- Abdominal ultrasound examination to exclude any renal anomalies.
Estimation of glomerular filtration rate using Schwartz formula 
K is constant=0.45 for FT NB.
- Fetal ultrasound examination to rule out any fetal anomalies.
- Serum creatinine.
The data were analyzed using a paired t test, the Pearson coefficient, and the Wilcoxon signed ranks test.
| Results|| |
This study included 50 healthy NBs, with a male to female ratio of 1 : 1; 54% were delivered vaginally and the remaining by cesarian section.
The gestational age of most of the neonates (88%) ranged from 38 to 40 week gestational age (WGA); 8% were 37 WGA, while 4% were 41 WGA. Apgar score assessment at 1, 5, and 10 min age was normal (8–10) in all the NBs studied.
Birth weight and length of all the NBs studied were in the normal range.
Systemic examination and abdominal ultrasound of all the studied cases were normal.
[Table 1] shows that blood film values of studied NBs were within the normal reference range. C-reactive protein values of all the studied NBs were within the normal range between 0 and 6 mg/dl, with a mean of 4.38±1.72 mg/dl.
|Table 1 Complete blood picture, C-reactive proteins, and hepatic enzymes of the studied newborns|
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Liver function tests (alanine transaminase, aspartate transaminase) of the studied NBs were within the normal range ([Table 1]). Maternal serum creatinine ranged from 0.4 to 0.69 mg/dl, with a mean of 0.54±0.09 mg/dl. There was no significant difference between maternal serum creatinine and NB serum creatinine on the first day of life ([Table 2]).
|Table 2 Comparison between maternal and neonatal serum creatinine on the first day of life|
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On comparing NB serum creatinine on the first and seventh days of life, there was a marked reduction in serum creatinine on the seventh day of life, which was highly significant ([Table 3]).
|Table 3 Serum creatinine level of the studied newborns on the first and seventh days of life|
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On calculating and comparing GFR on the first and seventh days of life, there was a marked increase in GFR by the seventh day of life, and the difference was statistically significant ([Table 3]).
There was a negative correlation between serum creatinine level and gestational age of NBs on the first and seventh days of life ([Table 4]).
|Table 4 Correlation between serum creatinine level and the newborns gestational age on the first and seventh days of life|
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The correlation between NB gestational age and GFR on the first and seventh days of life was positive ([Table 4]).
| Discussion|| |
From the 10th week of gestation and throughout intrauterine life, the kidneys produce increasing amounts of urine, a major constituent of amniotic fluid. However, in utero, the kidneys do not play a significant role in maintaining fetal homeostasis. This function is almost exclusively taken over by the placental fetal − maternal exchange .
The aim of the present work was to evaluate the renal function in the healthy full-term NB during the first week of life (days 1 and 7).
This study was carried out on 50 healthy full-term NBs delivered at Damanhour Medical Institute. The male to female ratio was 1 : 1. The gestational age ranged from 37 to 40 weeks of gestation.
In the present study, the mean serum creatinine at birth was significantly higher than that on the seventh day of birth. There was no significant difference between maternal serum creatinine (0.54±0.09) and that of NB on the first day of life.
Serum creatinine of NBs on the first day of life was expected to be equal to maternal serum creatinine, but it was higher; this was insignificant. The abruptness with which placental function is terminated by birth makes it necessary for the kidneys that are nearly normal in utero to respond to the functional demand of extrauterine life .
Because of the free passage of small chemical particles across the placenta, the concentration of basic biochemical markers of the baby at the time of birth equilibrate those of the mother. The creatinine level of NBs at birth reflects maternal serum creatinine . On the seventh day, it reflects exclusively the NB serum creatinine. The rapid significant decrease of serum creatinine during the first week of birth may be due to a significant increase in the RBF, decrease in renovascular resistance, and redistribution of the intrarenal pattern of glomerular blood flow .
The results of the present study were in agreement with those of Boer et al.  and others, who confirmed the rapid decrease of serum creatinine during the first week of life ,. Hoseini et al.  reported that plasma creatinine is high at birth and decreased by the first week of life; thereafter, it decreases more slowly to reach 0.4 mg/dl by the second week after birth. On calculating GFR, the current study showed a marked and significant increase in GFR from birth (34.2±4.9 ml/min) to the seventh day of life (53.5±4.8 ml/min). The results were in agreement with those obtained by Manzar et al.  and others, who reported a mean value of GFR of 31.8±15 ml/min of NBs at birth. Hoseini et al.  reported that GFR doubles during the first 2 weeks of life and reaches 50 ml/min − between the second and fourth week after birth.
At birth, systemic blood pressure is low, and the intravascular renal resistance is high, resulting in much-reduced kidney perfusion. The kidneys of NB receive only 15–20% of cardiac output, in contrast to the 25% of cardiac output observed in adults . This hypoperfusion, in combination with severely limited filtration surface, is the basic reason for the very low GFR of the NB .
In the present study, GFR was not affected by the weight and length of the studied NBs. This is in agreement with Boer et al. , who did not find an influence of weight and length on the level of serum creatinine and GFR of healthy full-term NBs.
The present study revealed a positive correlation between the GFR and the postnatal age of NBs between the first and seventh days of life. This finding was in agreement with others ,.
It was concluded that GFR increases within the first month of life. Preterm infants have a lower GFR compared with term infants and a lower rate of improvement of GFR is expected from the 34th to 36th week of gestation, and then the increase is significant, as seen in the first week of life in full-term NBs. It is necessary for the clinician to track postnatal changes in GFR at different gestational ages, so that they can recognize abnormal changes early, diagnose kidney failure and adjust medication doses, detect kidney damage precociously, and allow prompt interventions that might prevent future and more severe irreversible damage based on GFR changes.
This research was supported by the Alexandria University Faculty of Medicine.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]